CONSULT WITH YOUR VET FIRST! I don't know what your mini has but I'm sure that there are probably many other medications too that are probably not as harmful or dangerous.
You have to be careful with Penicillin and you have to make sure your horse (or mini horse!) has no known Allergies towards it or other related antibiotics such as Oxacillin. Also make sure you are not giving it to treat a 'cold' because it will not do the trick as Penicillin is an antibiotic.
Usually 1ml per 100lb, twice a day. ALSO MAKE SURE THAT YOU ARE EXPERIENCED. IF YOU HIT YOUR HORSE'S (OR MINI HORSE'S) VEIN IT CAN KILL THE HORSE. IT CAN ONLY BE GIVEN INTRAMUSCULARLY, IF YOU SEE ANY RED GET YOUR NEEDLE OUT!
You should not give a horse oral Penicillin. Oral Penicillin can seriously disrupt normal microorganisms in the digestive tract which can cause diarrhea and abdominal pain (colic). For an abscessed tooth you may need to give Injectable Penicillin, but never oral. It would be best to contact a equine veterinarian and possibly an equine dentist, as the tooth may need to be removed.
The amount of penicillin and the length of time to give it will vary somewhat with the brand used. It would be best to consult with a equine veterinarian regarding dosage and length of use.
First you should have a farrier and veterinarian come out and inspect the hoof for deeper infection. Once this has been done the equine vet will be able to give you exact dosage and time limits on the penicillin.
You should not give horses Penicillin for a cold, as a cold is caused by a virus and Penicillin is an Antibiotic and is not designed to treat a cold. You must let the cold run it's course, just like in a human.
I believe that the weight limit was about 100 lbs. give or take a few pounds.
You give the exact amount prescribed by your veterinarian. If your veterinarian has not prescribed penicillin for your puppy, you should not give any to your puppy. Penicillin is a drug with known side effects, including severe gastrointestinal bacterial infections from killing off the beneficial bacteria in the gut.
$10,000 to $100,000 depending on the horses background
Im not a beliver in 'breeding down' animals, but minis can carry children, pull carts, be cute :), there are national 'mini horse shows', seeing eye ponies, and much more
I use hay. It depends on how old your horse is on how much much you give them. My horse is 3 and I give 3 flakes, my sister's is 8 and she gives him four, but it depends on your preference
A mini can eat 1 to 2 flakes of hay a day and doesn't need grain. It depends on how much pasture you have and how much hay costs where you live.
Depends on what you are treating them for
This will depend on the penicillin product you are using and the type of condition you are treating. Different products contain different concentrations of the drug and even different forumlations which require different dosages. There is often a dosing range and the veterinarian makes a recommendation on the dose to use in a given situation based upon the type of condition/infectious organism being treated. Consult your veterinarian to determine an appropriate dosage in a given situation or if penicillin is even the appropriate drug for use in that situation.